Melanin spots on fillets are the result of the salmon's immune response to inflammation caused by stress or tissue damage.
Photo: Turid Mørkøre / Aker BioMarine.
The quality of the final salmon flesh is key to ensuring profitable production and the appearance of the fillet is one of the main factors influencing the consumer's purchasing decision. Melanin spots in Atlantic salmon fillets lead to product downgrades, reduced yields, and increased processing costs, therefore, avoiding them is one of the industry's current concerns.
A recent study conducted by a team of scientists in Aker BioMarine has gathered some research on melanin spots affecting salmon. They concluded that including a krill-based ingredient rich in essential fatty acids in the salmon diet can significantly reduce these dark spots, improving fillet quality and helping producers maximize their profits.
Melanin is a pigment naturally present in salmon in the form of dark spots on the skin of the fish. Also known as melanosis, these melanin spots on fillets are the result of the fish's immune response to inflammation caused by stress or tissue damage and are also a common quality problem.
Spots must be removed at the processing plants, increasing labor costs, and if the fillet has a diffuse pigmentation, the final product becomes of inferior quality or even discarded altogether, which also translates into economic losses for producers.
According to information provided by Aker BioMarine, just in Norway, up to 20 % of the harvested salmon is affected by melanosis, while in Chile, melanin spots are responsible for almost 30 % of the degradations, according to a study by Aquabench.
The appearance of melanin spots in salmon flesh is related to chronic inflammation of the musculature, which in animals has been related to prolonged exposure to stress. Diseases, adverse climatic conditions, and handling procedures are some of the different stress factors to which Atlantic salmon are subjected in intensive farming.
To combat this chronic inflammation, one way is to provide the fish with sufficient omega-3 fatty acids in the form of EPA and DHA. Essential for regulating inflammation, these fatty acids are part of the immune system's anti-inflammatory pathways and can prevent the possibility of an inflammatory process becoming chronic. Made from dried Antarctic krill, the aqua feed ingredient developed by Aker BioMarine, QRILL Aqua, provides these fatty acids in a phospholipid form that is more easily absorbed by fish.
Recent studies, including the 2022 EX-spot report, confirmed that increased levels of EPA and DHA in salmon feed significantly reduce the severity of melanin spots. Meanwhile, in-house research trials at Aker BioMarine using QRILL Aqua further confirmed that EPA and DHA levels in the feed influence the severity of dark spots on fillets and that the addition of krill meal to the diet can eliminate the appearance of melanin spots on fillets.
Specifically, the study showed that including 7.5% QRILL Aqua in the diet of salmon can eliminate melanin spots in fish weighing between 1.2 to 3.2 kg. Furthermore, according to Aker BioMarine studies, this krill-derived ingredient is key to improving the overall health of salmon.
The krill company claims that research has demonstrated its ability to increase feed intake, improve growth performance, reduce mortality rates, and increase fish robustness, resulting in a high-quality product.